1. Field of the Invention
The present invention relates to a high-frequency module in which a circuit element, such as a switch IC including a plurality of terminal electrodes, is mounted on a multilayer substrate.
2. Description of the Related Art
With the increase in sophistication and functionality of communication modules, such as mobile telephones, the need to transmit/receive communication signals in different frequency bands with a single antenna has arisen. In response to this need, various high-frequency modules each of which includes a switch IC have been proposed.
In a high-frequency module disclosed in Japanese Unexamined Patent Application Publication No. 2004-282727, a switch IC is mounted on a multilayer substrate so as to define a mounting component. Various circuits connected to terminals of the switch IC are disposed in the multilayer substrate. These circuits are defined by electrode patterns on and in the multilayer substrate and a mounting component.
The switch IC includes an antenna common terminal and a plurality of RF terminals, and is arranged to switch among the RF terminals to be connected to the antenna common terminal. Terminal electrodes defining the terminals of the switch IC are provided along sides of the switch IC chip.
As disclosed in Japanese Unexamined Patent Application Publication No. 2004-282727, lands are provided on the multilayer substrate at locations corresponding to the locations of the terminal electrodes of the switch IC. A line pattern extending from each of the lands is provided on the multilayer substrate.
The line pattern connected to each of the lands extends from the land in a direction away from the switch IC.
However, in the high-frequency module disclosed in Japanese Unexamined Patent Application Publication No. 2004-282727, the following problem arises. FIG. 8 is a diagram illustrating a problem that arises when lead line patterns in the related art are used.
As illustrated in FIG. 8, RF terminal lands 101 to 105 for a switch IC (SWIC) are arranged on a multilayer substrate at regular intervals along a side of the switch IC. Lead electrodes 201P to 205P extend from the RF terminal lands 101 to 105, respectively. The lead electrodes 201P to 205P include a portion arranged to extend in a direction away from the side of the switch IC (an oval region represented by a broken line in FIG. 8.) In this region, the lead electrodes 201P to 205P are parallel to one another. The intervals at which the lead electrodes 201P to 205P are arranged are equal to the intervals at which the RF terminal lands 101 to 105, that is, the terminal electrodes of the switch IC, are arranged.
When a signal is transmitted through one of the lead electrodes, a magnetic field is generated around the lead electrode and is coupled to another one of the lead electrodes adjacent to the lead electrode. That is, the isolation between these lead electrodes is deteriorated. In particular, in currently available small-sized high-frequency modules, the size of a switch IC is also relatively small. Accordingly, the intervals at which lands for the switch IC are arranged are relatively short, that is, a lead electrode formation pitch is relatively small. This deteriorates the isolation between lead electrodes.